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Unified Turbulence and Convection Scheme Progress Report - COSMO General Meeting 2007

The outline covers goals, participants, work achievements, encountered problems, and detailed plans for the coming year of the project focusing on turbulence, convection, and cloud parameterization.

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Unified Turbulence and Convection Scheme Progress Report - COSMO General Meeting 2007

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  1. The UTCS Project(Towards Unified Turbulence - Shallow Convection Scheme) Dmitrii V. Mironov German Weather Service, Offenbach am Main, Germany dmitrii.mironov@dwd.de COSMO General Meeting Athens, Greece, 18-21 September 2007

  2. Outline • The project goals • The project participants, work programme, schedule • Results obtained to date • Problems encountered • Detailed plan for the coming COSMO year (incl. resources required, schedule, milestones)

  3. The Project Goals • Parameterisation of boundary-layer turbulence and shallow non-precipitating convection in a unified framework of the second-order closure model • A better coupling between turbulence, convection (including triggering of deep convection), and radiation • An improved forecast of clouds, 2m temperature, and precipitation

  4. Work Programme, Schedule • Analytical derivation of the two-equation second-order turbulence-shallow convection closure scheme (UTCS), including transport equation for the sub-grid scalar variance • Coupling of UTCS with the sub-grid scale statistical cloud scheme • Development of a one-dimensional UTCS code, testing the UTCS through single-column numerical experiments, comparison with available empirical and numerical data • Implementation of UTCS into COSMO-model • Investigation of the interaction of UTCS with the radiation, grid-scale microphysics and deep convection schemes, slowing down deep convection scheme as needed • Testing UTCS in COSMO-model through numerical experiments, fine tuning UTCS parameters, evaluation of results • The project is scheduled for five years

  5. Project Participants • DWD, Germany: Jochen Förstener, Dmitrii Mironov, Matthias Raschendorfer, Axel Seifert, Gerd Vogel • MCH, Switzerland: Marco Arpagaus, Matteo Buzzi • CIRA, Italy: Pietro Catalano, Gabriella Ceci, Paola Mercogliano, Pier Luigi Vitagliano • ARPA Piemonte, Italy: Massimo Milelli, Antonella Sanna • HNMS, Greece: Euripides Avgoustoglou, Yannis Papageorgiou • NMA, Romania: Liliana Velea • IMGW, Poland: Grzegorz Duniec, Witold Interewicz

  6. Results Obtained to Date Review of turbulence-convection parameterisations in the lower troposphere (D. Mironov) Extended documentation of the existing COSMO-model turbulence scheme (M. Raschendorfer) Reconsideration and testing of the sub-grid scale statistical cloud scheme of the COSMO model (E. Augustoglou, Y. Papageorgiou) Slowing down the COSMO-model (Tiedtke) deep convection scheme (A. Seifert, D. Mironov)

  7. Problems Encountered: Delays (*) The project implementation has been considerably delayed Reasons: • Uncertain situation with the project leader • Shortage of human resources

  8. Problems Encountered: Personnel • DWD, Germany: Jochen Förstener, Dmitrii Mironov, Matthias Raschendorfer, Axel Seifert, Gerd Vogel • MCH, Switzerland: Marco Arpagaus, Matteo Buzzi • CIRA, Italy: Pietro Catalano, Gabriella Ceci, Paola Mercogliano, Pier Luigi Vitagliano • ARPA Piemonte, Italy: Massimo Milelli, Antonella Sanna • HNMS, Greece: Euripides Avgoustoglou, Yannis Papageorgiou • NMA, Romania: Liliana Velea • IMGW, Poland: Grzegorz Duniec, Witold Interewicz

  9. Work Planned for the Coming COSMO Year(September 2007 through September 2008) Tasks (i) Development, coding and testing against LES and observational data of a two-equation model of a temperature-stratified PBL; comparison of two-equations (TKE + TPE) and one-equation (TKE only) models (ii) Testing the existing sub-grid scale statistical cloud scheme in case that scheme is used by both the turbulence scheme and the radiation scheme of the COSMO model (iii) Comparison of the cloud condensate predicted by the sub-grid scale cloud schemes (statistical and relative-humidity) and by the grid-scale saturation adjustment procedure (iv) Testing modifications in the COSMO-model deep convection scheme (Tiedtke)

  10. Work Planned for the Coming COSMO Year(September 2007 through September 2008) Task (i): development, coding and testing against LES and observational data of a two-equation model of a temperature-stratified PBL; comparison of two-equations (TKE + TPE) and one-equation (TKE only) models Key issues: parameterisation of the pressure terms in the Reynolds-stress and the scalar-flux equations and of the third-order turbulent transport in the equations for the kinetic and potential energies of fluctuating motions, realisability, stable performance of the two-equation model Expected outcome: counter gradient heat flux in the mid-PBL, improved representation of entrainment at the PBL top Resources required: D. Mironov (analytical work - ongoing, realisability, stability issues, coding), NN (numerics, stability issues, coding, testing) Milestones: • March 2008 – analytical work performed • June 2008 – coding finished • September 2008 – two-equation model tested in single-column mode, comparison with data and with one-equation model performed

  11. Work Planned for the Coming COSMO Year(September 2007 through September 2008) Task (ii):Testing the existing sub-grid scale statistical cloud scheme in case that scheme is used by both the turbulence scheme and the radiation scheme of the COSMO model Key issues: consistency with the microphysics scheme (in particular, when the cloud ice is present), removing ad hoc “stopgap” formulations from the COSMO-model code, tuning as needed to harmonise the sub-grid scale cloudiness and the radiation calculations Expected outcome: a more consistent treatment of the sub-grid scale cloudiness within the COSMO model (eventually, an improved prediction of partial cloud cover and of the surface heat budget) Resources required: NN (E. Augustoglou and Y. Papageorgiou ?) Milestones: • February 2008 – test runs performed, results analysed • July 2008 – stopgap formulations removed (replaced with more physically justified formulations), tuning performed • September 2008 – (subject to successful verification of results from test runs) statistical cloud scheme is ready to be used in both turbulence and radiation calculations

  12. Work Planned for the Coming COSMO Year(September 2007 through September 2008) Task (iii):Comparison of the cloud condensate predicted by the sub-grid scale cloud schemes (statistical and relative-humidity) and by the grid-scale saturation adjustment procedure Key issues: difference in fractional cloudiness predicted by the relative-humidity and the statistical cloud schemes in various regimes (from broken cumuli with low fractional cloudiness to stratus deck with fractional cloudiness close to one), difference in the grid-box mean amount of cloud condensate predicted by the sub-grid scale cloud schemes and by the grid-scale saturation adjustment procedure in various regimes Expected outcome: a necessary prerequisite for improving/tuning the statistical sub-grid scale cloud scheme, and for eventually replacing the grid-scale saturation adjustment procedure with a procedure that accounts for the sub-grid scale processes Resources required: NN (L. Velea ?) Milestones: • December 2007 – additional diagnostics in the COSMO-model formulated and coded • May 2008 – test runs performed, predictions by different schemes in various regimes examined • September 2008 – comparison with observational data performed (whenever possible), results analysed and classified

  13. Work Planned for the Coming COSMO Year(September 2007 through September 2008) Task (iv): Testing modifications in the COSMO-model deep convection scheme (Tiedtke) Modifications: (a) cloud water-cloud ice mixed phase in convective clouds is allowed over a certain temperature range, (b) detrained convective cloud condensate is saved as tendencies of the cloud water and of the cloud ice, these are then passed to the COSMO-model physics and dynamics schemes for further processing (the current formulation assumes instantaneous evaporation of detrained convective cloud condensate), (c) convective trigger function is modified to account for the bulk properties of the sub-cloud layer, (d) formulations of turbulent entrainment and detrainment rates are extended to account for the updraught-environment buoyancy difference Expected outcome: improved prediction of heavy precipitation, better coupling of convection and microphysics schemes, deep convection slowed down (in particular, as the resolution is refined) Resources required: A. Seifert, D. Mironov [testing modifications (a) and (b)], NN [testing modifications (c) and (d)] Milestones: • February 2008 – modifications (a) and (b) tested, results from parallel experiments verified (work is underway at DWD) • December 2007 – modifications (c) and (d) introduced into the COSMO-model code • September 2008 – modifications (c) and (d) tested

  14. Work Planned for the Coming COSMO Year(September 2007 through September 2008) Resources required (persons/NNs; FTEs; necessary qualification) Task (i): • D. Mironov; 0.6 FTE; expertise in turbulence and convection modelling • NN; 0.5 FTE; expertise in numerics, good programming skills (F90 is a must), background knowledge of turbulence modelling Task (ii): • NN; 0.5 FTE; knowledge of SGS cloud parameterisations in NWP atmospheric models, acquaintance with the COSMO-model code, good programming skills, experience in running COSMO model • NN; 0.4 FTE, qualifications same as above + knowledge of radiative transfer schemes Task (iii): • NN; 0.5 FTE; knowledge of SGS cloud parameterisations of the COSMO model, acquaintance with the COSMO-model code, good programming skills, experience in running COSMO model, experience in using non-standard observational data for NWP model testing/verification Task (iv): • NN; 0.4 FTE; background knowledge of mass-flux cumulus convection parameterisations for NWP models; acquaintance with the COSMO-model code, good programming skills, experience in running COSMO model and verifying the model results

  15. Work Proposed … NB Tasks (ii) and (iii) do not require any results from new development (output from the UTCS Tasks 1 and 2)  all necessary bits and pieces are already available in the COSMO-model code. Theses tasks were formulated in March 2007 and were presented during the meeting in Langen. Project participants were asked to take on the responsibility for (ii) and (iii). No concrete suggestions so far.

  16. Outlook • Enough resources should be allocated, the project participants should make a firm commitment to perform the work • The UTCS concepts/ideas are now hopefully clear (DM’s paper and MR’s documentation should help!) • The project participants are requested (begged!) to show more initiative and to be more creative • The project leader is at your disposal for guidance

  17. Thanks for your attention!

  18. Work Plan beyond 2008 (2008 through 2010) Task [schedule]; persons/NNs, FTEs, qualification required (i) Development, coding and testing against LES and observational data of a two-equation model of moist PBL with non-precipitating clouds (UTCS), comparison of two-equations (TKE + TPE) and one-equation (TKE only) model [July 2008 – July 2009] • D. Mironov; 0.7 FTE; expertise in turbulence and convection modelling • NN, 0.7 FTE; expertise in numerics, good programming skills (F90 is a must), knowledge of turbulence and convection modelling, experience in using observational and numerical (LES) data for model verification (ii) Implementation of UTCS into the COSMO model [February 2009 – September2009] • 2xNN; 0.6 FTE each; knowledge of turbulence and convection schemes, acquaintance with the COSMO-model code, good programming skills (F90 is amust), experience in running COSMO model (iii) Investigation of the interaction of UTCS with the radiation, grid-scale microphysics and deep convection schemes, slowing down deep convection scheme as needed [January – June 2010] • 2xNN; 0.5 FTE each; knowledge of turbulence, convection, radiation and microphysics schemes, acquaintance with the COSMO-model code, good programming skills (F90 is amust), experience in running COSMO model (iv) Testing UTCS within COSMO-model through numerical experiments, fine tuning UTCS parameters, evaluation of results [September 2009 – December 2010] • 3xNN, 0.5 FTE each; background knowledge of turbulence and convection parameterisations for NWP models; acquaintance with the COSMO-model code, good programming skills, experience in running COSMO model and verifying the model results

  19. Results Obtained to Date (cont’d) Extended documentation of the existing COSMO-model turbulence scheme (M. Raschendorfer) • An extended documentation of the COSMO-model turbulence parameterisation scheme is prepared. It includes an outline of basic concepts, a description of the current turbulence scheme, a number of extensions (most notably, a stable boundary-layer turbulence parameterisation) that make the COSMO-model scheme distinct from the standard Mellor-Yamada type one-equation turbulence closure, and an outlook. The documentation is a necessary pre-requisite for further development within the framework of the UTCS project. Along with DM’s paper, it should aid the members of the COSMO Physical Aspects Working Group (perhaps the members of the other Working Groups as well) in their work on testing/tuning of the existing COSMO-model physical parameterisation schemes.

  20. Results Obtained to Date (cont’d) Reconsideration and testing of the sub-grid scale statistical cloud scheme of the COSMO model (E. Augustoglou, Y. Papageorgiou) • The sensitivity of the COSMO-model performance to variations of the disposable parameters of the cloud scheme, to changes in the COSMO-model horizontal mesh size, and to the inclusion of the cloud ice scheme in combination with the statistical cloud scheme is tested. It is found, among other things, that the inclusion of cloud ice scheme has a profound effect on results (see the presentation by E. Augustoglou and Y. Papageorgiou). Slowing down the COSMO-model (Tiedtke) deep convection scheme (A. Seifert, D. Mironov) • Several modifications to the Tiedtke scheme are tested through parallel experiments with the COSMO-EU of DWD. The prime objectives are to avoid strong overestimation of heavy precipitation and to achieve a better coupling between the deep convection and the microphysics schemes. The proposed modifications do remedy the situation with heavy precipitation. The average performance of the COSMO-model, e.g. with respect to medium-to-small amount of precipitation, is slightly deteriorated over some periods of time. The cause of the problem is being investigated.

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